Be on Alert for 'Super Toxic' Bug in Travelers, CDC Says

E coli Infection 'Very Rare' but Deadly

Nancy A. Melville

June 03, 2011

June 3, 2011 — As health officials in Germany continued to seek the source of a uniquely toxic enterohemorrhagic Escherichia coli outbreak that has claimed the lives of at least 18 people, the Centers for Disease Control and Prevention (CDC) issued a notice to healthcare providers to be on alert for the Shiga toxin–producing E coli O104:H4 (STEC O104:H4) infections among travelers returning from Germany.

While there are some reports of the outbreak stabilizing, the World Health Organization (WHO) confirms that a total of 1823 cases of STEC O104:H4 have been reported, including 520 cases of hemolytic uremic syndrome (HUS), a potentially life-threatening complication of the infection that can cause kidney failure. Twelve HUS cases were fatal, and 6 deaths were reported among non-HUS cases.

The number of countries reporting cases of the STEC O104:H4 poisoning had increased to 11 on Friday. However, all but 1 of the deaths since the outbreak emerged in May have occurred in Germany. The 18th death was reportedly in Sweden and involved a person who had recently returned from Germany.

Symptoms of the strain, which European authorities have called "super-toxic," are notably severe, including stomach cramps, bloody diarrhea, vomiting, and fever. However, fever is not usually high.

Rare but Not Unfamiliar

Four suspected cases of the infection have been reported in the United States, all involving people who had recently traveled to Hamburg, Germany, said Chris Braden, MD, Director of Foodborne, Waterborne, and Environmental Diseases for the CDC, at a press briefing today.

Three of the 4 cases in the United States involved HUS and the patients were hospitalized. "The fourth case did not develop HUS but had bloody diarrhea, and we know there was a Shiga toxin–producing organism involved," he said.

Dr. Braden described the STEC O104:H4 strain as "very rare" but not entirely unfamiliar.

"The CDC is not aware of any confirmed cases of this infection ever reported in the US. However, we have become aware of similar strains in other countries in the past," he said.

The strain attacks the body in a manner unlike other strains of Shiga-producing E coli.

"The strain is different in its genetic markers and in the way it attaches to the lining of the intestine," Dr. Braden added.

Most Victims Female

In addition to causing particularly severe symptoms, the strain is unusual in that most of its victims appear to be women and people over the age of 20.

"It is true that in Germany 60% of the enterohemorrhagic E coli cases and 71% of the HUS cases are female," the WHO confirmed.

The unusual patterns underscore that little is known about the strain's unusual nature, but they could also suggest the source that may be somehow related to the adult female demographic, Dr. Braden said.

"We have a lot to learn about this particular organism. It's possible this organism had a predilection for adults over children, but it's also possible the type of food or produce is being eaten [more] by adult women than others."

Dr. Braden also noted that the duration time from exposure to onset of symptoms is also unique, with incubation times of more than a week to up to 12 days, compared to as little as 5 days commonly seen with other E coli infections.

Most patients' symptoms resolve within 5 to 7 days. However, HUS can develop a week after diarrhea begins.

"The classic triad of findings in HUS is acute renal damage, microangiopathic hemolytic anemia (evidence of schistocytes and helmet cells on peripheral blood smear), and thrombocytopenia," the CDC explained in a statement.

Prime Suspects

After backtracking on an earlier suggestion that the source of the E coli strain could be linked to organic Spanish cucumbers, German officials maintain that cucumbers, tomatoes, and lettuce are top suspects.

In addition, the Robert Koch Institute, Germany's national disease control agency, has advised consumers, particularly those in the northern Germany region around Hamburg, to avoid those vegetables.

The Institute has said that the number of cases appeared to have peaked around May 21 or 22. However, officials cautioned that communication delays may have slowed the reporting of new cases since then. In the meantime, German officials are not letting their guard down.

"We are dealing here in fact with the biggest epidemic caused by bacteria in recent decades," Reinhard Brunkhorst, president of the German Nephrology Society, told reporters in Hamburg this week.

In treating suspected STEC cases, some research has shown that administering antibiotics may in fact increase their risk of developing HUS, but the CDC recommends that clinicians ultimately determine treatment according to each individual patient.

"There may be indications for antibiotics in patients with severe intestinal inflammation if perforation is of concern," the agency said. "Of note, isolates of STEC O104:H4 from patients in Germany have demonstrated resistance to multiple antibiotics."

Detection Guidelines

The agency issued the following additional guidelines for detecting and characterizing STEC infections:

  • All stools submitted for testing from patients with acute community-acquired diarrhea should be cultured for STEC O157:H7. These stools should be simultaneously assayed for non-O157 STEC with a test that detects the Shiga toxins or the genes encoding these toxins.

  • Clinical laboratories should report and send E coli O157:H7 isolates and Shiga toxin–positive samples to state or local public health laboratories as soon as possible for additional characterization.

  • Specimens or enrichment broths in which Shiga toxin or STEC are detected, but from which O157:H7 STEC isolates are not recovered, should be forwarded as soon as possible to a state or local public health laboratory so that non-O157:H7 STEC can be isolated.

  • It is often difficult to isolate STEC in stool by the time a patient presents with HUS.  Immunomagnetic separation (IMS) has been shown to increase recovery of STEC from HUS patients. For any patient with HUS without a culture-confirmed STEC infection, stool can be sent to a public health laboratory that performs IMS or to the CDC (through a state public health laboratory).  In addition, serum can be sent to CDC (through a state public health laboratory) for serologic testing of common STEC serogroups.

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